It is widely known that various organometallic compounds and asphaltenes are present in petroleum crude oils and other heavy hydrocarbon streams, such as petroleum hydrocarbon residua, hydrocarbon streams derived from tar sands, and hydrocarbon streams derived from coals. The most common metals found in such hydrocarbon streams are nickel, vanadium, and iron. Such metals are very harmful to various petroleum refining operations, such as hydrocracking, hydrodesulfurization, and catalytic cracking. The metals and asphaltenes cause interstitial plugging of the catalyst bed and reduced catalyst life. The various metal deposits on a catalyst tend to poison or deactivate the catalyst. Moreover, the asphaltenes tend to reduce the susceptibility of the hydrocarbons to desulfurization. If a catalyst, such as a desulfurization catalyst or a fluidized cracking catalyst, is exposed to a hydrocarbon fraction that contains metals and asphaltenes, the catalyst will become deactivated rapidly and will be subject to premature removal from the particular reactor and replacement by new catalyst.
Catalysts comprising one or more metals selected from Group VIB and Group VIII of the Periodic Table of Elements, alumina, and oxides of phosphorus are known, which catalysts can be used for various hydrotreating, hydrocracking, and demetallization processes.
Hamner, et al., in U.S. Pat. No. 3,928,176, disclose the hydroconversion and hydrodenitrogenation of heavy hydrocarbon streams in a two-catalyst process. Each of the two catalysts comprises a hydrogenation component of a Group VIB metal and/or a Group VIII metal on a support, such as alumina, silica, zirconia, magnesia, boria, titania, ceria, and thoria. The preferred support for the first catalyst is alumina and is a large-pore support. The same support materials can be employed in the second catalyst; however, they are in admixture with aluminum phosphate. The second catalyst is a small-pore catalyst and always includes an aluminum phosphate component, preferably in concentrations ranging from about 30% to about 100%. Hamner, et al., teach that the preferred small-pore aluminum phosphate catalyst includes a combination of properties comprising at least about 90%, and preferably at least about 99%, of its total pore volume of absolute diameter within the range of about 1.5 nm (15 Angstrom units [.ANG.]) to about 10.0 nm (100 .ANG.), and less than about 5%, and preferably 2%, of its total pore volume of absolute diameter within the range of about 8.0 nm (80 .ANG.) to about 15.0 nm (150 .ANG.). The pore volume of this aluminum phosphate catalyst ranges from about 0.25 cc/gm to about 0.75 cc/gm. While the Hamner, et al., patent teaches a process which employs two catalysts, the second catalyst of which contains aluminum phosphate, it does not teach a catalyst having an average pore diameter that is greater than 12.5 nm (125 .ANG.) and containing a high-surface area support comprising catalytically active alumina and one or more oxides of phosphorus.
Anderson, et al., in U.S. Pat. No. 2,890,162, teach that suitable additives may be used to promote pore size distribution growth and/or for acting as active catalytic components of the finished contact agents. This patent discloses that various metals, mixtures of metals, metal compounds or mixtures of metal compounds, or of one or more metals and one or more metal compounds are suitable as such additives. They disclose that the materials may or may not be in chemical combination with the porous solid on the surface thereof. They list phosphates as one of the suitable metallic agents for such purposes. They provide that such promoters are present in an amount of about 0.1 wt% to about 10 wt%, preferably 0.5 wt% to about 5 wt%, although amounts greater than that may be employed if desired. They teach that the catalysts of their invention are quite suitable for hydrocracking residua and other asphalt-containing materials to lower boiling distillates and oils. They do not suggest that such a catalyst would be suitable for the hydrodemetallization of heavy hydrocarbon streams.
Pine, in U.S. Pat. No. 3,904,550, discloses the preparation of alumina-aluminum phosphate catalyst support materials by reacting an aluminum alkoxide with an aqueous solution containing phosphate ions and their use in hydrocarbon conversion processes, such as catalytic cracking, hydrocracking, hydrofining, and reforming. He teaches the combination of his alumina-aluminum phosphate support with hydrogenation metals, for example, with 0 to 50wt%, usually 20 to 30 wt%, of any of the Group VIB and Group VIII metals for use in the desulfurization and denitrogenation of light and heavy petroleum fractions and with 0 to 60 wt%, usually 10 to 25 wt%, of any of materials known to promote hydrocracking reactions, which include, inter alia, nickel oxide, cobalt oxide, molybdenum oxide, tungsten oxide, and zeolites for use in hydrocracking. His alumina-aluminum phosphate support contains from 35 to 85 wt%, and preferably from 50 to 75 wt%, aluminum phosphate. He does not consider a catalyst for hydrodemetallization.
Long, et al., in U.S. Pat. No. 3,989,645, disclose two different catalyst compositions, each of which has a pore size distribution that is different from the pore size distribution of the other catalyst that is disclosed in the patent. Either catalyst comprises a hydrogenation component comprising a Group VIB metal or a Group VIII metal, or both, on a suitable porous refractory inorganic oxide. The inorganic oxide supports suitably comprise alumina, silica, zirconia, magnesia, boria, phosphate, titania, ceria, thoria, and the like. The preferred support is alumina. This patent presents several catalysts that have an alumina support and contain 1 wt% P.sub.2 O.sub.5, the phosphorus having been introduced into the composites by means of phosphomolybdic acid. Either catalyst can contain from about 5 wt% to about 50 wt%, preferably about 15 wt% to about 25 wt%, Group VIB metal and about 1 wt% to about 12 wt%, preferably about 4 wt% to about 8 wt%, Group VIII metal. These catalysts can be used in hydroconversion processes, which include demetallization.
Kehl, in U.S. Pat. No. 4,080,311, discloses thermally stable amorphous composite precipitates containing aluminum phosphate and alumina and having a surface area of about 100 m.sup.2 /gm to about 200 m.sup.2 /gm and an average pore radius of 7.5 nm (75 .ANG.) to 15.0 nm (150 .ANG.). He teaches that such thermally stable composite precipitates contain from 10 to 60 mole % alumina and from 40 to 90 mole % aluminum phosphate. He indicates that the term "composite" is used to denote the new compositions which are not physical admixtures. He discloses that the alumina-aluminum phosphate composite precipitates are suitable for use in catalytic cracking or for use as catalyst supports in reactions such as hydrogenation wherein a hydrogenation metal or metals from Group VI and/or Group VIII are deposited on the surface of the alumina-aluminum phosphate.
Eberly, in U.S. Pat. No. 4,003,828, teaches that increased catalytic activity for demetallization of metal-contaminated hydrocarbon feedstocks is realized for catalysts containing phosphorus oxides. Eberly discloses that the phophorus oxide is present in an amount within the range of 1 to 6 wt%, preferably 1.1 to 5.5 wt%, expressed as P.sub.2 O.sub.5 and based on the weight of alumina and phosphorus oxide (the support). Only Catalyst D in the examples contains a P.sub.2 O.sub.5 content that is greater than 6 wt%. However, that catalyst contains as hydrogenation metals both cobalt and molybdenum and their combined amount, expressed as oxides, is at least 15 wt%. In addition, Catalyst D has a pore volume that is less than 0.7 cc/gm. Eberly suggests that the phosphorus promotes increased pore size.
Choca, in U.S. Pat. No. 4,066,572, considers a phospha-alumina composition having a large pore diameter of at least 10 nm (100 .ANG.) and a pore volume distribution with a minimum number of small pores, i.e., less than 30% of the total pore volume being in pores smaller than 10 nm (100 .ANG.) in diameter. She discloses that such a composition may be used as catalyst supports for various combinations of cobalt, nickel, tungsten, and/or molybdenum for use in the desulfurization and denitrogenation and other hydrotreating processes of both light and heavy petroleum fractions, or in combination with zeolites for use in hydrocracking or catalytic cracking, or combined with noble metals for reforming. She indicates that the average pore diameter increases with the amount of phosphorus introduced into the composition in its preparation and that total pore volume decreases with increasing amounts of phosphorus. In Example V, she furnishes a catalyst that contains 8 wt% P.sub.2 O.sub.5 and was prepared to contain 14 wt% MoO.sub.3 and 3 wt% CoO, which catalyst was employed as a catalyst for the hydrodesulfurization of a heavy vacuum gas oil.
Choca, et al., in U.S. Pat. No. 4,132,669, disclose phosphorus-containing catalysts that are prepared by using polycarboxylic acids, such as citric acid, as extrusion aids. They indicate that the phospha-alumina powders of the invention generally comprise anywhere from 3 wt% to 30 wt% P.sub.2 O.sub.5. In addition, they disclose that the support material can be impregnated with catalytically active metals, such as cobalt, nickel, molybdenum, and tungsten and suggest in the introduction of the patent that alumina-phosphorus materials are useful for hydrotreating catalysts, hydrocracking catalysts, demetallization catalysts, and the like.
Cull, in U.S. Pat. No. 4,233,184, discloses a high-surface area aluminum phosphate-alumina product that is a suitable catalyst support and that is prepared by reacting a mixture comprising aluminum alkoxide and an organic phosphate in the presence of moist air to form a precipitate, separating the precipitate from the mixture, and drying and calcining the precipitate. Although steam is present during the preparation of the precipitate, there is no disclosure of the heating of the product in the presence of steam to increase the average pore diameter of the product in the absence of any appreciable reduction in pore volume.
In U.S. patent application Ser. No. 946,499, Hopkins, et al., disclose a process for the hydrometallization of a hydrocarbon feedstock containing asphaltenes and a substantial amount of metals, which process employs a catalyst comprising a small amount of a hydrogenation component comprising at least one active original hydrogenation metal deposed on a large-pore, high-surface area support comprising catalytically active alumina and one or more oxides of phosphorus, said phosphorus being present in an amount that is greater than 6 wt%, calculated as P.sub.2 O.sub.5 and based upon the weight of the support. There is no discussion directed to the steaming of such a catalyst or to the use of a steamed catalyst.
Steam treatment can be used to control or improve the performance of a catalytic material. For example, catalysts are often steam deactivated in preparation for testing. An example of this is presented by Michalko in U.S. Pat. No. 3,531,397, in column 7, at lines 62 through 73.
It is well known in the art that catalysts can be treated with steam for the purpose of improving catalytic properties and performance. For example, Plank, et al., in U.S. Pat. No. 3,140,253, at column 12, lines 3 through 16, consider a preliminary steam treatment of cracking catalysts comprising crystalline aluminosilicates at temperatures within the range of 427.degree. C. (800.degree. F.) to about 816.degree. C. (1,500.degree. F.) to provide improved selectivity and other beneficial properties. O'Keefe, et al., in U.S. Pat. No. 3,668,114, provides a method for improving the attrition resistance and heat stability of a silica-alumina catalytic cracking catalyst wherein the catalyst can contain up to 35 wt % alumina, which method comprises treating the catalyst with steam of a temperature within the range of about 482.degree. C. (900.degree. F.) to abut 816.degree. C. (1500.degree. F.) for at least 1/2 hour under a steam pressure of about 1 to 25 atmospheres. In U.S. Pat. No. 3,530,065, Leaman, et al., consider the cracking of hydrocarbons in the presence of a siliceous conversion catalyst including a catalyst selected from amorphous siliceous catalysts and those containing a minor or major portion of a material comprising a catalytically active crystalline aluminosilicate and in column 2, at lines 55 through 65, indicate that a preliminary steam treatment of such catalysts will achieve a desired stabilization of catalyst activity and selectivity. In the U.S. Pat. No. 3,382,189, Mitchell, et al., disclose the heat treatment of fluidizable particles of a silica-alumina catalyst first in a moisture-free atmosphere and then in a substantially oxygen-free steam-rich atmosphere when the temperature of the particles is above a temperature at which steam condensation will take place in order to provide a material that has improved activity, selectivity, and resistance to deactivation by temperature and steam. In the U.S. Pat. No. 3,933,621, White, et al., disclose the steaming of silica-alumina catalysts at a temperature of 1,400.degree. F. to provide improved cracking catalysts.
Chessmore, et al., in U.S. Pat. No. 4,199,435, teach the steam treatment of a metallic carbon monoxide combustion-promoting catalyst prior to its use with a fluidized cracking catalyst in a catalytic cracking regeneration operation to decrease the amount of NO.sub.x formed during regeneration of the cracking catalyst that is present with the combustion-promoting catalyst. Such combustion-promoting catalyst comprises one or more combustion-promoting metals, such as platinum, palladium, iridium, rhodium, osmium, ruthenium, rhenium, and copper, associated with a particulate solid inorganic oxide, such as silica, alumina, silica-alumina, silica-magnesia, or a zeolite-containing material. Such steaming is carried out at a temperature of 760.degree. C. (1,400.degree. F.) to 1,100.degree. C. (2,012.degree. F.) and a steam pressure of 1 to 15 atmospheres for a period of 2 to 100 hours.
Kearby, in column 12, at lines 4 through 10, of U.S. Pat. No. 3,342,750, in considering the preparation of high-surface area aluminum phosphate gels, discloses that the high-temperature steaming of such a gel does not decrease the surface area of the gel to as great an extent as does water impregnation of the gel. There is no indication as to how pore volume or average pore diameter are affected by such steaming.
While the art has suggested that various catalytic materials can be steamed for various purposes, there has been no disclosure of the use of steam to increase the average pore diameter of a composite of alumina and one or more oxides of phosphorus in the absence of decreasing appreciably the pore volume of the composite.
Now it has been found that the treating of a composite of alumina and one or more oxides of phosphorus with steam at an elevated temperature will provide a catalytic material that has increased pore size without an appreciable change in pore volume and is useful for making a demetallization catalyst having improved activity maintenance.
Not one of the above-discussed patents discloses the steam-treatment of a composite of alumina and one or more oxides of phosphorus wherein the pore size of the composite is increased without an accompanying appreciable reduction in pore volume.